What spring and (maybe) a plunger depends on the age of the gun. Post a partial serial number. On older guns it's on the butt. On newer ones it's stamped on the frame under the barrel. You have to swing out the cylinder to see it.

First 3 ser# are 769** and the only thing under the cylinder is Mod 66-1. Funny thing is, the only thing I recall being behind the hammer stop is a piece of old half round plastic that crumbled when I touched it.

The S&W model 66-1 was made between 1977 through 1982. I would expect the serial number to have two digits followed by the letter "K" and then the rest of the number. For example (56K46xxx).

The cylinder bolt in your revolver does use a small coil spring and plunger, and Brownells will have them (Their part numbers 940-070-200 and 940-070-980).

I'm not sure what you mean by "hammer stop" and I don't believe S&W was putting anything in the lockwork that was made of plastic, at least at this time. There was a trigger stop in some guns. Perhaps someone else added something?

OH, ok, I was looking at the bottom of the grip handle, but on the side of the bottm strap., which that # is also on the side plate. The # on the bottom of the grip handle is 21K8***. Yes, thanks for the # to the plunger and spring. I entered "cylinder bolt and spring" in the search function and got 1000 different things. Now I know to punch in S&W K frames and pull up the schematic and it lists all the parts one can order. Also, I don't know, Jerry Kuhnhausen calls it the cylinder bolt/hammer stop and says it's a double duty piece with the front being the cylinder pivot and the back end being the hammer stop. The only thing I can figure , as far as the plastic piece behind the bolt, was that it wasn't plastic at all, but maybe glue that the factory squirted in there to keep the plunger and spring in place. The bottom of the main spring was embedded in some kind of glue, as well.

A "21Kxxx" serial numbered should have been made in 1977. When ordering parts it's always a good idea to provide a partial serial number because over the years manufacturers make changes. But when you do this be sure you have a complete and correct number or someone on the receiving end could be badly mislead.

There is a lug on the back of the cylinder bolt that prevents the hammer from being cocked when the cylinder is opened. This insures that the ratchet hub can't batter the hand, which is extended when the hammer is cocked. From your description I wasn't sure if someone had added something in the way of a non-factory accessory/part or not.

Regarding the "glue" or whatever. This is something the factory would never do, and who ever did do it wasn't too bright. Be sure that all traces of it are cleaned out before you replace the spring & plunger. I would also inspect the rest of the lockwork for any foolish tampering or "trigger pull/action" work. Check for a shortened mainspring strain screw and cut-off rebound block spring. You may need to order additional parts besides the cylinder bolt spring & plunger.

It would be nice if the gun manufacturers could decide to use the same words to describe identical kinds of parts.

Yes, the hammer stop prevents when the cylinder is open , but also when the cylinder is closed but the cylinder pin didn't get lock up in the frame.

I checked the mainspring screw and the rebound slide spring and found nothing amiss, so I don't know.

Also, I was wondering how the plunger and spring does stay in place, as I see only a half round cylinder cut out in the frame and the back of the bolt is half round, so what's to keep the plunger from sliding back and forth( assuming the plunger goes against the frame and the spring goes against the bolt).

If it isn't filled with glue (or whatever) there is a hole drilled in the back of the cylinder bolt that the spring and plunger fit into. The spring goes in first and part of the plunger is left sticking out. Your Kaunhausen manual will show how to disassemble and reassemble these parts. The plunger does indeed push agains the back of the cylinder bolt cut-out in the frame.

If you close the cylinder and the cylinder's center-pin doesn't push the bolt backwards something is wrong - perhaps seriously wrong. This would indicate a sprung yoke, or maybe some more "glue" in the works.

Grreat googly moogly, There's a little round raised nipple on the back of the bolt and I took an ice pick and pushed on it , lo and behold, the spring and plunger popped out. Btw, were these guns packed in grease? Could the'glue or whatever' been old , hardened grease?

Anything is possible, and if the gun had been made in the 1930's or earlier I'd say it was likely. However on a revolver made during the late 1970's I'd say it was unlikely. S&W didn't put heavy grease in their revolvers - especially stainless steel guns at this time. They were lightly oiled and wrapped in vapor inhibitor paper (VIP). However anything could have happened after it left S&W. I would advise that a complete and through cleaning is in order.

Onlike some Colt's, the S&W doesn't "lock solid." If it did a little dirt or fouling could cause the stop to skip a notch. Excessive play is more often caused by movement of the stop inside the "window" or slot in the frame rather then between the notch and the stop's "ball." I usually consider the movement to be excessive if the cylinder can be moved more then .003" each way. For more information see your manual.

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